JPS63136919A - Protective pipe for underground burial cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a protective pipe for underground cables made of plastic, and in particular, a protection pipe for underground cables made of plastic that has excellent heat resistance, impact resistance, weather resistance, and moldability. Regarding protective tubes for cables.

[Prior art and the problems it attempts to solve] It has been known to mold a resin composition mainly composed of vinyl chloride resin and use it as a protective pipe for power cables buried underground. Some vinyl chloride resin pipes reinforced with additives have already been put into practical use.

However, since ordinary vinyl chloride resin has low heat resistance, when used as a protective tube for cables with large power capacity, it becomes soft due to heat generation and cannot withstand earth pressure or live loads such as trucks, making it useless. Put it away. Therefore, it is only used as a protective tube for thin cables with relatively low power capacity, and steel pipes and humid tubes are currently used as protective tubes for large-capacity cables. However, steel pipes are heavy and have poor workability in piping work, and hume pipes are also heavy and vulnerable to impact from pickaxes and the like.

Recently, attempts have been made to use post-chlorinated vinyl chloride resin to improve the heat resistance of vinyl chloride resin.
Although this chlorinated vinyl chloride resin pipe has excellent heat resistance, it has the drawbacks of poor impact resistance, moldability, and weather resistance.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a protective tube for underground cables made of plastic and having excellent heat resistance, impact resistance, weather resistance, and moldability.

[Means for solving problems]

The present invention solves the above-mentioned problems by using a structural unit derived from vinyl chloride in an amount of 50 to 99% by weight, and a general formula (
1) [wherein R is a substituted or unsubstituted aliphatic, alicyclic or aromatic group having 1 to 30 carbon atoms; R' and R
# may be the same or different and is a hydrogen, fluorine, chlorine or bromine atom, a cyan group, or an alkyl group having 3 or less carbon atoms. This invention provides a protective pipe for underground cables made of plastic molded using a copolymer containing 1 to 50% by weight of a structural unit derived from N-substituted maleimide represented by the following formula.

In this specification, the term "protective tube for underground cables" refers not only to a tubular molded product obtained by molding the copolymer or a composition containing the copolymer, but also to a bent product obtained by secondary processing of this. Refers to all tubular objects such as pipes, sleeved pipes, and connecting pipes.

The copolymer used in the present invention is composed of vinyl chloride and the general formula (1
) with an N-substituted maleimide in the presence of a free radical-generating catalyst.

Specific examples of the N-substituted maleimide of general formula (1) include N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-t-butyl Maleimide, N-hexylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-p, m or 0-hydroxyphenylmaleimide, N-p, m or 0-methoxyphenylmaleimide, N-p, m or 0-chlorophenylmaleimide, N-p
, m or 0-carboxyphenylmaleimide, N-p, m or. -nitrophenylmaleimide, N-laurylmaleimide, N-bicyclo-(2,2,1)-hebutan-1-yl-
Examples include 3-methylmaleimide, N-9,10-ethano-9,10-dihydroanthracen-2-ylmaleimide, N-)riphenylmethylbenzylmaleimide, and particularly preferred ones include R being methyl,
t-Butyl, cyclohexyl, bicyclo-(2,2,1
)-hebutan-1-yl-3-methyl, 9. Examples include lO-ethano-9,10-dihydroanthracenyl, triphenylmethylbenzyl, and the like.

The copolymer used in the present invention has a structural unit derived from vinyl chloride in an amount of 50 to 99% by weight, preferably 70 to 95% by weight.
and the structural unit derived from the N-substituted maleimide of general formula (1) is 1 to 50% by weight, preferably 5 to 30% by weight.
It is. If the content of the structural unit derived from N-substituted maleimide in the copolymer is less than 1% by weight, it is difficult to improve the heat resistance of the copolymer, and if it exceeds 50% by weight, the resulting copolymer The melting temperature is too high, resulting in poor moldability.

In the method for producing a copolymer of the present invention, at least one type of polymer to which other polymerizable monomers and vinyl chloride can be graft-polymerized can be used as a raw material, if necessary.

Other polymerizable monomers include vinyl esters such as vinyl acetate, vinyl caproate, vinyl laurate, and vinyl stearate, olefins such as ethylene, propylene, and isobutylene, isobutyl vinyl ether, octyl vinyl ether, dodecyl vinyl ether, and phenyl. Alkyl vinyl ethers such as vinyl ether, halogenated olefins such as vinylidene chloride, vinyl fluoride, propylene chloride, vinyl bromide, ethyl acrylate, n-
Butyl acrylate, n-butyl methacrylate, 2-
Examples include acrylic acid and methacrylic acid esters such as ethylhexyl acrylate, 2-ethylhexyl methacrylate, and stearyl methacrylate, and acrylic derivatives such as acrylic acid, methacrylic acid, crotonic acid, acrylonitrile, maleic anhydride, and itaconic anhydride. be done. These are not limited to one type, and two or more types may be used simultaneously.

Polymers that can be graft-polymerized with vinyl chloride include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, and chlorinated polyethylene (C
PE), polyurethane, polybutyl acrylate, butyl rubber, polystyrene, crosslinked acrylic rubber, and the like.

The polymer to which the other polymerizable monomers and vinyl chloride can be graft-polymerized has a component derived therefrom of 30% by weight or less, preferably 15% by weight, in the resulting copolymer.
It is preferable to use it so that it is less than % of heavy background. If the component derived from these components exceeds 30% by weight, the original characteristics of polyvinyl chloride resin, such as high mechanical strength and durability, will be lost.

In the production of the copolymer, the amount of raw materials used is adjusted so that the constituent parts derived from each raw material monomer and the polymer used in some cases in the resulting copolymer are in the above-mentioned proportions.
It is possible for those skilled in the art to easily control the polymerization conditions as appropriate. For example, the desired composition can be achieved by monitoring the amount of each monomer charged and the reaction rate of a specific monomer. A copolymer of can be produced.

The copolymer can be produced by any method such as bulk polymerization, suspension polymerization, emulsion polymerization, etc.
Generally, suspension polymerization is industrially and economically advantageous. Polymerization is generally carried out at about 20 to 80°C in the presence of a free radical generating catalyst.

As the free radical generating catalyst used in the polymerization, those commonly used in the polymerization of vinyl chloride can be used, such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, di(isopropyl) peroxydicarbonate. , diacyl peroxides such as di(2-ethylhexyl) peroxycarbonate, acetylcyclohexylsulfonyl peroxide, tert-butyl peroxyvivalate, tert-
Organic peroxides such as peroxy esters such as butylperoxyneodecanate, and α,α′-azobisisobutyronitrile, α,α-azobis-2゜4-dimethylvaleronitrile, α,α′- azobis-4-methoxy-
Examples include azo compounds such as 2,4-dimethylvaleronitrile, and water-soluble peroxides such as potassium persulfate and ammonium persulfate, and these can be used alone or in combination of two or more.

As the polymerization method, the suspension polymerization method is preferable as described above, but the suspension stabilizer used in that case may be one that is normally used in the polymerization of vinyl chloride monomers. Stabilizers include fully saponified or partially saponified polyvinyl alcohol, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, polyvinylpyrrolidone, and synthetic polymer compounds such as maleic anhydride-vinyl acetate copolymer. Natural polymer substances such as , starch, and gelatin are exemplified, and these are not limited to one type, but two or more types may be used in combination.

The protective tube for underground cables made of plastic of the present invention includes:
Although the above copolymer can be molded alone, it can also be used for molding as a composition formed by blending it with other polyvinyl chloride resins. When used as a composition with other polyvinyl chloride resins, the general formula (1
) is required to have a content of the structural unit derived from N-substituted maleimide in the range of 1 to 50% by weight.

Examples of polyvinyl chloride resins that can be used in combination with the copolymer of the present invention include, in addition to vinyl chloride homopolymers, copolymers of vinyl chloride and ethylene, propylene, etc., and ethylene-vinyl acetate copolymers. Polymers, ethylene-ethyl acrylate copolymers, multi-component copolymers obtained by graft copolymerizing vinyl chloride onto ethylene polymers such as chlorinated polyethylene, and blends thereof are also included.

When the above-mentioned copolymer or a composition of the copolymer and a polyvinyl chloride resin is molded into the protective tube of the present invention, a stabilizer and, if necessary, a lubricant, an impact modifier, and a processing aid are added. , filler, pigment, etc. are mixed in a mixer, and the mixture is kneaded in an extruder or the like and molded.

Stabilizers that can be used include, for example, metal salts such as calcium, cadmium, barium or zinc laurates or stearates, and soaps; tribasic lead sulfates, dibasic lead phosphites, dibasic phthalates. acid lead,
Lead stabilizers such as lead white, lead laurate and stearate; di-n-alkyltin mercaptide, di-n-alkyltin dilaurate, diptyltin dimaleate, dibutyltin lauryl mercaptide, dioctyltin-s, s'-
Bis-(isooctyl-mercaptoacetate), diptyltin bis-isooctyl-toglycolate, di(n
-octyl)tin maleate polymer, tin stabilizers such as dibutyltin mercaptopropionate; antimony stabilizers such as antimony mercaptocarboxylate or ester salts; and phosphates.

Examples of lubricants include metal soaps, stearic acid, glyceryl monostearate, ethyl diaminostearate, paraffin, and low molecular weight waxes.

As an impact modifier, it is necessary to select one that does not particularly impair heat resistance or weather resistance due to its properties, such as ethylene-vinyl acetate copolymer (EVA), chlorinated polyethylene, ethylene-acrylic acid. ethyl copolymer,
Examples include ethylene-propylene copolymer (EPR), crosslinked acrylic rubber, and multi-component modifiers in which monomers such as methyl methacrylate, styrene, and acrylonitrile are graft-polymerized to polyacrylic esters, and the amount used is limited. In view of the correlation between the above-mentioned other properties required for the protective tube of the present invention, the amount is preferably 3 to 20 parts by weight per 100 parts by weight of the copolymer of vinyl chloride and Ni-converted maleimide of general formula (1).

In addition, heat resistance improvers such as acrylonitrile-α-methylstyrene-butadiene copolymer, PMMA and acrylic acid ester copolymer, and other processing aids and fillers commonly added to vinyl chloride resins, A fuel agent, a smoke suppressant, an antioxidant, etc. may be added within a range that does not impair the purpose of the present invention.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

The test method for each characteristic in this example is as follows.

Tensile test: According to JIS K-6739.

Heated needle test: Charpy impact strength: Based on JIS-7111.

Weather resistance: According to JIS^-1415, exposed for 100 hours using an S-type accelerated exposure device at a black panel temperature of 63 ± 3 °C and spraying for 18 minutes/120 minutes, and then measured according to JIS K-7111 after exposure. It is shown as the value of Charpy impact strength according to the method.

Moldability: Visually observe the surface condition of the molded product.

Evaluation criteria for moldability ◎ Two surfaces are smooth and uniform with no flow marks or uneven gloss.

08 The surface is smooth with almost no flow mark unevenness observed.

68 Flow mark uneven gloss is observed on the surface.

×: The surface is not smooth and has large flow marks and uneven gloss.

Example 1 In a 1d autoclave, 270 kg of vinyl chloride, 30 kg of cyclohexylmaleimide, 550 kg of pure water, and G2
- 240 g of ethylhexyl peroxydicarbonate,
and 300 g of partially saponified polyvinyl alcohol were charged and reacted at 50° C. for 7 hours. After recovering unreacted monomers, the reaction mixture was dehydrated and dried to obtain a vinyl chloride-cyclohexyl maleimide copolymer.

The cyclohexylmaleimide content in the copolymer was 12% by weight as a result of chlorine analysis.

Next, additives were added to 100 parts by weight of this copolymer in the proportions shown below, and 2007! The mixture was uniformly mixed by a conventional method using a Henschel mixer, and a pipe with an inner diameter of 75 mφ and a wall thickness of approximately 6 mm was extruded using a 75 mm diameter twin screw extruder in different directions. The properties of the obtained pipe were evaluated using the method described above.

Examples 2 to 4 Polymerization was carried out in the same manner as in Example 1, except that the compounds shown in Table 1 were used instead of N-cyclohexylmaleimide, and pipes were formed. The characteristics of the obtained pipe were evaluated in the same manner as in Example 1. The results are shown in Table-1.

Examples 5 to 7, Comparative Examples 1 and 2 The total amount of vinyl chloride and N-cyclohexylmaleimide is 300 kg, and the ratio of both monomers is such that the ratio of N-cyclohexylmaleimide is as shown in Table 1. Polymerization was carried out in the same manner as in Example 1, except for the following changes, and a pipe was molded and evaluated. The results are shown in Table-1.

Comparative Example 3.4 Puffs were molded in the same manner as in Example 1, except that ordinary vinyl chloride homopolymer or chlorinated vinyl chloride resin was used instead of the copolymer produced in Example 1, respectively. evaluated. The results are also shown in Table 1.

〔Effect of the invention〕

The protective tube for underground cables made of plastic according to the present invention has excellent heat resistance, which was inferior to conventional protective tubes made of vinyl chloride resin materials, and also has high impact resistance, weather resistance, moldability, etc. It has characteristics. Therefore, it can be suitably used not only as a power cable with a small power capacity but also as a protective tube for a cable with a large power capacity. In addition to being lightweight, it has high impact resistance and weather resistance, making it easier to perform underground burial work.
It also has excellent long-term durability.

Claims (1)

[Claims] 50 to 99% by weight of structural units derived from vinyl chloride, and general formula (I) ▲There are numerical formulas, chemical formulas, tables, etc.▼...(I) [In the formula, R is a carbon atom 1 to 30 substituted or unsubstituted aliphatic, alicyclic or aromatic groups; R' and R
'' may be the same or different and is a hydrogen, fluorine, chlorine, or bromine atom, a cyan group, or an alkyl group having 3 or less carbon atoms.] Structural unit 1 derived from an N-substituted maleimide represented by
A protective tube for underground cables made of plastic molded using a copolymer containing ~50% by weight.